Method of making concrete blocks and the like



NOV. 5, 1940. A, HENDERSQN i l2,220,448

-METHD OF MAKING CONCRETE BLOCKS AND THE LIKE Fled'Aug. 5, 1938 {NVENTORAZberzHeJzdefJoJz Patented Nov.v 5, 1940 UNITED STATES METHOD F MAKINGCONCRETE BLOCKS AND THE LIKE Albert Henderson, Edgewood, ra., minor toWilliam P. Witherow, Pittsburgh, Pa.

Aopuomon August s, 193s, sensi No. 223,34

Clalms.

This invention relates to the manufacture of molded cementitiousarticles such as blocks,

slabs. etc., and, particularly, to a method of maklng such articleswhereby they may be produced 5 more cheaply than heretofore and at thesamev time be characterized by superior quality.

This is a continuation in part of my copending application, Serial No.62,965, filed February 8, 1936, for Apparatus for making concretearticles,

now Patent No. 2,131,474, granted September 2'7,

Concrete blocks and the like have usually been made heretofore bytheso-called dry process. While this process produces blocks 'which aresatisfactory for many uses such as foundation wallsand the like whereappearance is a secondary consideration, the blocks so made have notbeen used widely in exposed locations.' Further'objectlons to theprevious method of making blocks include the high labor cost resultingfrom the necessity for handling the blocks individually from the moldsto storage piles, as well as the danger of chipping and breakageresulting from such handling. The prior practice has been to 23 storethe blocks for aging in any convenient place, without protection fromthe weather or changes in atmospheric temperature. This causesdiscoloration of the blocks and renders them generally undesirable fromthe standpoint so of appearance.

and novelty which will become apparent as the following detaileddescription of the invention proceeds. In a preferred practice of theinvention, I pour liquid concrete into gang moldsr preferably from atraveling hopper. The hopper may conveniently be supplied with concretefrom a truck mixer. The blocks or other articles are partly cured in themold and then removed therefrom to a curing chamber for final curing.After curing, the blocks are dipped to chill them and stored in the sameroom where molded and cured whereby the waste heat from the molding andcuring operations prevents the blocks from being subjected during agingto dangerously low temperatures. A complete understanding of the 5oinvention may be obtained from the following Referring in detail tol thedrawing, I prefer to carry out the molding, curing and aging of blockswithin a single room or building as indicated by slde walls I0, roof Iland suitable end walls. A bridge crane I2 traversing the length 5 of thebuilding facilitates transfer of-the blocks from point to point therein.

,An aisle I3 extends the length of the building, conveniently along oneside thereof, and is provided with a paved roadway Il for the passage 10therealong of a vehicle adapted todeliver mixed concrete, the usual formof such vehicle being a truck mixer as indicated diagrammatically at Il.As is well-known, these vehicles are charged with sand, cement,aggregate and water at cenl5 tral hatching plants and eiect thenecessary mixing of such materials while en route to the point 'ofdelivery.

`Molding apparatus indicated generally at I8 is arranged alongside theaisle I3. This appa- 20 ratus is preferably such as that more fullydescribed and claimed in the parent application above referred to.Briefly. it comprises side rails I1 along which a traveling hopper I8moves.

Gang molds I9 are spaced along the side rails 25.

and adapted to receive concrete from the hopper in its various positionsas it travels along the rails. A water tank 20 is installed beneath thegang molds and is provided with steam pipes 2l whereby heat and moisturemay be supplied to so the space surrounding the molds.

In accordance with the invention, concrete is discharged from the truckmixer I5 to the hopper I8 through a chute 22 periodically orcontinuously as may be desired. The hopper I8 dls- 35 charges concreteto one gang mold I! until the latter is filled to the desired level.Thereupon .the truck mixer and hopper are moved along the aisle to thenext gang mold. If desired, a coupling may be provided between the mixerand 40 hopper so thatv the hopper is drawn along the side rails II bythe truck mixer in the manner of a trailer.

After the mold Il has been filled, it is subiected to vibration by anysuitable means to 45 density and compact the concrete in theA severalmold chambers. Steam is then admitted to the pipes 2l in such manner asto maintain the temperature adjacent the mold at about 175 F. 'I'hiscauses evaporation of the water in the tank 50 2li whereby the desiredmoisture content is maintained in the air adjacent the mold. The heatsupplied by the steam pipes 2| causes partial curing of the moldedarticles. If too much heat is supplied, the concrete may exhibitundesired expansion or flumngt This impairs the quality -of the nishedproduct. To prevent this result I subject the molded articles, afterpartial curing, to vibration or compression by any suitable means. andthus again density and compact the articles in the mold.

When the articles have set sumciently to be self supporting, whichcondition is attained in a relatively short time, because of therapidity at which curing proceeds in the temperature maintained adjacentthe mold, I partially remove the articles from the chambers of the mold,by means of the apparatus described and claimed in the parentapplication referred to above. This breaks the bond between the articlesand certain of the mold parts and thereby facilitates the final removalof the articles from the mold.

A final curing chamber is located alongside the mold I9 and mayconveniently take the form of a liftable,`open-bottomed box 22.Buccessive layers of articles formed in the mold il are deposited over awater tank 24 having steam pipes 2l therein and enclosed by the cover 22forming a final curing chamber. Steam is supplied to the pipes 25 insuch manner as to maintain in the chamber a temperature even higher thanthat to which the articles were initially.

subjected, e. g., 225 to 250 l". I have found that molded concretearticles, after initial curing, may safely be exposed to suchtemperature to accelerate the completion of the curing cycle withoutdanger of expansion orfflumng.

On completion of the curing, the articles are separated from the moldportions which were removed from the mold with them to provide a unitaryliftable mass including a plurality of articles, and piled on skips 2lfor further handling en masse. In order to prevent excessive dehydrationof the heated 'articles on exposure to the air, by evaporation of suchfree water as remains in them, I dip them in a tank` 2I of cold water.This dipping operation chills the blocks and thusprevents excessivedehydration on subsequent exposure to the air. Heat-exchange pipes 28may be connected to a convenient source of heating or cooling fluid tomaintain the bath in the tank 21 at the proper temperature. Instead ofplain water, the tank 21 may contain a. coloring, sealing or hardeningliquid.

Since the pores. of the articles are open when they are heated, suchliquids will readily penetrate the articles on dipping. After dipping,the skip loads of articles are piled as indicated at 29 for gradualshrinkage. This process as previously can'ied out required aconsiderable length of time. I reduce the time required for shrinkage bystoring the articles in the same room in which they are molded and curedand close enough to the heated molding and curing chamber so that thewaste heat therefrom maintains the blocks in storage at a temperature ofabove 40 F. and accelerates the shrinkage process.

'I'he articles produced in accordance with the individually. Thisprocedure is carried out even in delivering the articles to the job, asthe loaded skips 2| may conveniently be placed on a delivery truck andthe blocks removed at the job in the most convenient location. The emptyskips are then returned from the job for reloading.

'I'he vibration of the mold after initial curing of the articles thereinproduces a stronger product with a lower absorption coefficient than hasbeen obtainable heretofore. This is because the vibration eliminates thecells formed in the cement -paste by the quick hydration thereofresulting from heat applied in the curing. As already indicated, thechilling of the blocks when cured prevents excessive loss of moisturetherefrom and also permits the application of coloring, sealing orhardening agents. The sudden chilling of the articles produces noobservable ill effects. By protecting the articles during aging againstabnormally low temperatures, the

strength of the finished article is increased and an attractive colorimparted thereto, viz., al-- but a preferred practice -of my method, itwill be understood that changes in the procedure disclosed may be madewithout departing from the spirit of the invention or the scope of theappended claims.

I claim:

l. Inl method `of making concrete articles, the steps including poln'lngconcrete into the mold, vibra-ting the mold, heating the mold and theconcrete therein, and vibrating the mold and its contents after partialsetting of the latter.

2. In a method of making concrete articles, the steps including moldingthe articles, subjecting the articles to heat to accelerate thehydration of the cement in the concrete by the available water. and,before elimination of all the free water, wetting the articles with aliquid at a temperature substantially below that to which the articlesare heated, while they are hot from the curing, thereby chilling themand inhibiting excessive dehydration.

3. The method defined by claim 2 characterized by dipping the articlesin the water.

4. In a method of making concrete articles, the steps includingdepositing concrete in a mold, heating the concrete in the mold, therebyeffecting a partial curing of the article, vibrating the article toreduce the voids formed by the removal of surplus water in curing,removing the article from the mold, subjecting it to further heatingadjacent the mold to complete the curing, wetting the article while hotfrom the curing with water at a tempera-ture below that of the article,thereby cooling it and inhibiting excessive dehydration, and storing thearticle near enough to the mold so that the waste heat from the curingoperation expedites volume change in the article in storage.

5. In a method of making concrete articles, the steps includingdepositing a cementitious mix in. a mold, curing the formed articlesfbyapplying heat to the mold, said heat driving off surplus water in thearticles, and reducing the voids left by the removal ofsaid surpluswater, by vibrating the articles.

ALBERT HENDERSON.

